When a motor such as a DC motor or a stepping motor is driven with high efficiency, a motor current is controlled by a pulse width modulation (PWM) control using a half bridge circuit or a full bridge circuit and includes a charge current and a regeneration current. It is important to detect the motor current with high accuracy in a system for driving the motor.
A method of motor current detection in which a sense resistor is inserted between a motor and a drive circuit and a motor current is detected as a voltage between both ends of the sense resistor to be controlled, or a method in which a motor current is detected as a drain-source voltage of an output power MOS transistor of a drive circuit to be controlled, or the like is known.
In the method of using a sense resistor, an external resistor is used as the sense resistor and thus, there is a problem that it is not possible to reduce the number of components and in the method of using detection of a drain-source voltage of the output power MOS transistor, there is a problem that detection accuracy of a regenerative current is reduced.